A flange is a steel ring that is forged or cast to link pipe sections or unite pipe to a pressure tank, pump, or other integrated flange assembly. Bolting connects flanges to one another, and welding or threading connects flanges to the piping system. Stainless Steel Flanges (ss Flanges), Alloy steel flanges, Carbon steel flanges, Slip on, Blind, Weld Neck, and other types of flanges are the most common.